I'm going to sound like a broken record, as this has been suggested before (by myself and by others), but I feel like there should be a really nice / lucrative incentive for players to log in every day.

A good solid way to do this would be by offering some useful Mythic pet eggs available for purchase with story tokens. Arcane would be a bit much, but Mythic isn't unreasonable.

Of course, they should be difficult to obtain so as not to flood the market. I'm thinking 1200 tokens (which is roughly 4 solid months of bard dailies).